"While we are not going to speculate on reports that Pakistan may look to purchase used F-16s elsewhere, we would note that under US law, any re-transfers of US-origin defence items to a third party require approval from the US Government, may require Congressional notification, and would be subject to end-use monitoring," a State Department official told reporters.

The official, who requested anonymity, was responding to a question on reports that Pakistan is considering buying used F-16 jets from Jordan after its plan to buy eight of them from the US at a highly subsidised rates fell through because of the opposition from lawmakers in the US Congress who want Islamabad to take strong action against the Haqqani network.

"The proposed terms and conditions of the Letter of Offer and Acceptance for this proposed sale of F-16 aircraft expired on May 24," the official said. "Pakistan did not accept the offer to purchase F-16s from the United States, and the terms of the sale have expired," another State Department official told reporters.

"We are now going for a third-party transfer of F-16s and have an offer from Jordan," Pakistan Defence Secretary Alam Khattak had said last week.

"We refer you to the Government of Pakistan to speak to their decision and future defence procurement plans," the US official said when asked about Khattak's statement.

The official was not aware if the US has received such a request from Jordan and Pakistan. However, it is believed that there could be options for Pakistan to explore the possibility of procuring F-16 from the United States at its full price.

The earlier proposal of eight F-16s to Pakistan at an estimated cost of USD 699 million was heavily subsidised, to which the US lawmakers led by Senator Bob Corker, Chairman of the Senate Foreign Relations Committee had objected.

Informed sources argue that if Pakistan wants to pursue the sale, it could start a fresh talk with Lockheed Martin – the manufacturer – and negotiate a new full price for the F-16s it wants to buy.